By Erin Steele, Record-Gazette

Posted 1 day ago

There is an outbreak of Forest Tent Caterpillar in the Peace River area – visible by patches of trees void of green on Misery Mountain and throughout the valley – and caterpillar populations are set to increase over the next few years.

According to Mike Maximchuk, a forest health officer with Environment and Sustainable Resource Development (ESRD), this particular species will periodically outbreak, for a yet-unknown reason every seven to 10 years across Northern Alberta.

The last outbreak in Peace River, according to Maximchuk, ended in 1996.

“The Peace River area has been overdue for a forest tent caterpillar outbreak for quite some time,” he told the Record-Gazette by phone.

Typically an outbreak in any given area lasts between four and seven years, with the caterpillar population growing so exponentially that anything that could potentially downsize the population is deemed futile.

“All the parasites and predators and birds and so forth just can’t keep up with the reproductive capacity of the tent caterpillar. They just can’t control the populations,” Maximchuk said.

Now that they have arrived, the only thing that could potentially downsize populations in the first few years of an outbreak is if we get a late spring frost or snowfall, he added.

“And as they get bigger, they eat more and more leaves and so the pattern of defoliation becomes much greater, much faster. And they’ll still be feeding for probably at least two more weeks before the majority of them have finished feeding and turn into a pupae,” Maximchuk says.

The Forest Tent Caterpillar has hormones in its body that triggers when it has finished feeding. At this point they spin themselves a silk cocoon surrounded by yellow powder – ten days later the pupae hatches and turns into a brown moth, either male or female.

These moths’ sole purpose is to mate. They will lay eggs around the tips of branches and tops of trees, and there they will remain until next spring when they hatch as caterpillars.

According to Maximchuk, the caterpillars and their effect of defoliation will migrate across the landscape.

“It might move 30, 40 kilometres in a given year, sometimes more. And as they’re building more and more survive so population spreads into more and more areas as they move and as they grow,” Maximchuk said.

The caterpillars are expected to reach the pupae stage around the end of June, beginning July, with Peace River residents expected to see the unusually large amount of moths shortly after this time.

“Those brown moths will be attracted to lights on buildings, on people’s houses, on gas stations, on the grocery stores,” Maximchuk said.

The affected trees will re-grow a secondary set of leaves a couple weeks following the last of the caterpillar’s feeding to help them maintain their existence, though aesthetically it will not mirror the shade visible a few weeks ago, Maximchuk says, as the leaves of the second set are smaller.

Though the caterpillar species does not directly kill trees on its own, it does weaken them which makes the trees less resilient to other insects and diseases.

Forest Tent Caterpillars are found naturally in the forest, but usually in such low numbers they go unnoticed.

“And then something triggers their populations to increase exponentially. No one is really sure exactly what triggers it. It could be favorable weather conditions,” Maximchuk said.

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